During spermatogenesis in a variety of mammals including rats and humans a testis-specific Hl histone (Hlt) appears in conjunction with the process of meiosis. We propose to determine the complete amino acid sequence of Hlt in anticipation that this structural information will provide clues to its functional role. The sequencing approach will entail the production and isolation of a series of overlapping peptides and their sequence analysis by automated Edman degradation. In addition, we will determine whether Hlt is subject to phosphorylation or ADP-ribosylation, its precise cellular association by immunohistochemical techniques, and its pattern of interaction with certain non-histone chromosomal proteins. In a second area of investigation, we will isolate one or more specific proteins from structural elements of rat sperm tails. Such proteins will serve as markers to determine whether the synthesis of major spermatid components occurs on messenger RNA templates that originated in earlier stages of development such as meiosis. The study will involve purification of specific messenger RNA molecules, the preparation of radioactive cDNA copies from them, and the analysis of specific messenger species by RNA/DNA hydridization techniques. A search will be made for testicular proteins whose synthesis is regulated rapidly by testosterone or folicle stimulating hormone (FSH). The program involves use of 2-dimensional polyacrylamide gels, in vitro incorporation of radioactive amino acids by intact seminiferous tubules, and the preparation of animals in which spermatogenesis is arrested at critical hormone sensitive steps. Characterization of the mode of association of a spermatid-specific transitionary histone with chromatin will be proved by nuclease digestion experiments and the analysis of digestion products by 2-dimensional electrophoretic gels.